JPH0221962A - Coater - Google Patents

Abstract

PURPOSE:To prevent the leakage of the gas in the recess of an object to be coated into a coating liquid and the consequent formation of air bubbles by providing a gas discharge hole for discharging the gas in the recess according to the pressure of this gas at the time of immersing the object to be coated into the coating liquid. CONSTITUTION:The pressure in the hollow part (recess) 4c of a conductive base body drum 4 increases gradually when the base body drum 4 is immersed into the coating liquid 1. The air in the hollow part 4c is gradually released like an arrow A through a needle valve 8 according to the pressure increase. As a result, the leakage of the air in the hollow part 4c into the coating liquid 1 and the consequent formation of the air bubbles are prevented, by which the oscillation of the coating liquid is prevented and the generation of the unequal coated films is prevented. The uniform coated film is thus formed.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a coating apparatus, for example, a dip coating apparatus for coating and forming a photosensitive layer of an electrophotographic photoreceptor.

Conventional technology When coating and forming the photosensitive layer of an electrophotographic photoreceptor, it is necessary to maintain good sensitivity characteristics, prevent image defects such as density unevenness, and exhibit good performance as a photoreceptor. It is necessary to apply a uniform thin layer.

Conventionally, various coating methods such as dip coating, spray coating, spinner coating, wire bar coating, blade coating, and roller coating have been known as coating methods for the photosensitive layer of electrophotographic photoreceptors, but dip coating is the main method. and spray application is used.

Among these, dip coating is often used to form a uniform coating on a cylindrical object (such as a conductive substrate).

When coating the surface of a cylindrical conductive substrate (hollow one, hereinafter sometimes referred to as substrate 1-ram) using such a dip coating method, it is difficult to immerse the hollow substrate drum as it is. Since both ends are open, the coating liquid (paint) enters the hollow part of the base drum, and the coating liquid (=J) lands on the inner wall surface and is wasted.
In order to prevent this, the upper end of the base drum J is closed off when the base drum J is immersed.

FIG. 11 is a sectional view showing the timing of dip application by such a method.

Application I! A predetermined coating liquid 1 is contained in the coating liquid 1, and during dip coating, the base F ram 4 is immersed in the coating liquid 1 with the opening 4b facing downward. The upper end opening 4f of the base tram 4 is closed by a lid 5, and an O-ring 10 is provided between the outer peripheral surface of the lid 5 and the inner peripheral surface 4d of the base drum to prevent air leakage. When the substrate drum 4 is immersed, the coating 'a, 1 is removed from the hollow section 4c due to the air filling the hollow section 4c in the substrate tram 4, and the liquid level drops to position 1c. Then, the outer peripheral surface 4c of the base drum
is applied up to a height of 4a.

After the immersion is completed, the M5 handle 5a is grasped and the base drum 4 is pulled up at a predetermined speed, so that a coating film is formed on the outer circumferential surface 4e of the base drum up to a height 4a.

However, in such a coating device, the air in the hollow portion 4c may expand due to the temperature difference between the coating liquid 1 and the outside air temperature, or the solvent in the coating liquid 1 may evaporate into the hollow portion 4c. As a result, the air in the hollow portion expands as shown by the dashed line 1d, and bubbles 3 are often produced from the opening 4b side when the base drum 4 is pulled up. Then, the coating liquid 1 is shaken by the bubbles 3, causing unevenness in the coating film on the base drum 4, making it impossible to obtain a uniform coating film.

The following methods are known as methods for solving this problem.

(a), method described in Japanese Patent Application Laid-Open No. 59-80363 The lower end of a cylindrical base drum with both ends open is immersed in a coating liquid, and the coating liquid is penetrated into the hollow part of the lower end of the base drum. Sell. Thereafter, the upper end of the base drum is sealed, and the base drum is immersed in the coating liquid in this sealed state.

However, in this method, the opening of the substrate drum must be sealed when the substrate tram is immersed, which is complicated.

(b), Method No. 12 described in Japanese Patent Publication No. 62-4187
As shown in the figure, a pipe 9 is provided that passes through the side wall 2d of the coating tank, and one end of the pipe 9 has an opening 9a that is lower than the liquid level of the coating liquid.
so that it is located on one side. The other end of the pipe 9 is provided with a balloon-shaped expandable air chamber 28. When the base drum 4 is immersed, the air in the hollow portion 4c flows into the air chamber 28 through the pipe 9.
expands as shown by the solid line, and some of the air in the base drum 4c is removed. As a result, the coating liquid level slightly rises to a height of 1e. When the base drum 4 is pulled up, the air chamber 28 contracts as shown by the phantom line.

However, in this method, it is necessary to separately provide an air chamber outside the coating tank to store the evacuated air, which takes up space and is also disadvantageous in terms of cost.

(C), method described in Japanese Utility Model Publication No. 61-155071 As shown in FIG. 13, a pipe 9 is provided that penetrates the bottom surface 2c of the coating tank. Also, the opening 9a of the pipe 9 is shifted upward. In this state, open the valve 18 and open the hollow part 4.
The air in c is removed and the coating liquid level is raised to the height of position 1e.

Then, when raising the base drum 4, the valve 1
Close 8.

However, in this method, it is necessary to open and close the valve in synchronization with the dipping and lifting of the base drum, which is extremely complicated.

C1 Purpose of the Invention The purpose of the present invention is to easily and easily prevent the generation of bubbles due to the expansion of gas in the recesses of the object to be coated, and the occurrence of uneven coating due to this, without requiring unnecessary equipment. It is an object of the present invention to provide a coating device that is not required.

20 Structure of the Invention The present invention provides a method for applying the coating liquid by immersing an object to be coated having a recessed portion in a coating liquid contained in a coating tank and lifting the object to be coated relative to the coating liquid. A coating device for applying the above-mentioned material to the object to be coated, further comprising a gas discharge hole which itself has a function of discharging the gas in the recess according to the pressure of the gas when the object to be applied is immersed; The invention relates to a patented device characterized in that the gas to be discharged is discharged into an open system outside the coating tank.

Example The present invention will be explained in detail below.

In the following embodiments, members having the same functions as those of the conventional coating device are denoted by the same reference numerals, and the explanation thereof will be omitted.

'LjJ envelope l↓ FIG. 1 is a sectional view of the coating device, showing the state in which the base tram 4 is immersed in the coating tank 2. FIG. 2 is a sectional view showing the coating tank 2. FIG.

In this example, a through hole 5b is provided in M5, and a pipe 9 passes through the through hole 5b. The pipe 9 is provided with a needle valve 8, which is a distinctive feature.

That is, this needle valve 8 has a needle-shaped valve body, and has the function of gradually extracting the air in the hollow part 4c into the outside air according to the pressure in the hollow part 4C. Therefore,
Unlike the valve shown in FIG. 13, there is no need to perform opening/closing operations, and the air flow rate is automatically adjusted according to the pressure within the hollow portion 4c.

Next, the dipping and lifting operations of the base drum 4 will be described.

From the state shown in FIG. 2, the base drum 4 is immersed in the coating liquid 1 with the opening 4b facing downward, resulting in the state shown in FIG. 1. At this time, the pressure inside the hollow part 4C gradually increases,
In response to this, the air in the hollow portion 4C is gradually released as shown by arrow A through the needle valve 8. Then, the coating liquid level is raised to the height of position 1e. After this, the base tram 4 is raised to the state shown in FIG. 2. At this time, the pressure inside the hollow part 4C gradually decreases, but if this pressure is higher than atmospheric pressure, air is released as shown by arrow A, and if it is lower than atmospheric pressure, air is sucked in as shown by arrow A. . Eventually, the coating liquid 1 is removed from the hollow portion 4c, and the lifting of the base drum 4 is completed.

The type, material, etc. of the needle valve 8 can be selected as appropriate depending on the dimensions of the coating device, etc.

Next, preferred embodiments will be described.

When the base drum 4 is left in the immersed state, the liquid level of the coating wfL1 rises by 1 to the position 1f shown by the - dotted chain line. This raised position changes depending on the air discharge speed of the needle valve, the specific gravity of the coating liquid, the immersion time, etc.

By appropriately selecting the amount of air discharged from the needle valve, the upper boundary position 1e of the coating liquid level can be appropriately set by simply adjusting the needle valve first.

According to the coating device of this example, the following effects can be achieved.

(a) By the action of the needle valve, air can be removed according to the pressure inside the hollow part of the base drum, and the
, the pressure inside the hollow part can be adjusted easily and without much effort. Of course, there is no need for any extra operations such as conventional valve opening/closing operations and sealing operations on the upper end of the base drum. Therefore, the immersion and lifting of the base drum itself can be performed smoothly and continuously.

(b) Since the air in the hollow part of the base is automatically removed by the knee 1' leparve, the air in the hollow part expands,
Even if the solvent evaporates inside the hollow part, no air bubbles are formed. Therefore, it is possible to prevent the coating liquid from shaking and to prevent the occurrence of unevenness on the coating film.

(C) An air chamber like the one shown in FIG. 12, for example, is not provided on the opening side of the pipe 9, and air is vented by a needle valve 8. Therefore, the equipment is simpler, takes up less space, and is advantageous in terms of cost.

(d) In the electrophotographic photoreceptor, as a result of being able to prevent uneven coating on the coating film, it is possible to prevent image unevenness on the copied image and provide a uniform image.

Fig. 3(a) is an enlarged sectional view of a main part of another coating device, and Fig. 3(b) is a plan view showing the base drum and its surroundings.

In this example, by providing a small through hole 5d passing through the lid 5 and adjusting the diameter of the small through hole 5d, as in Example 1,
The pressure inside the hollow part of the base body is controlled.

The diameter of the small through hole is, for example, 50 μmφ to 1000 μmφ
It can be done.

(Q) According to this example, it is only necessary to provide a through hole of an appropriate size in the lid 5, which further simplifies the structure.

Disaster ±1 FIG. 4 is an enlarged sectional view of a main part showing still another coating device, and corresponds to No. 311(a).

In this example, a small through hole 5e is provided in the lid 5, a thin pipe 19 is passed through the small through hole 5C, and one end 1 of this pipe 19 is
9a is placed in the hollow portion 4c, and the other end 19b is placed in the outside air. By changing the diameter and length of the pipe 19, the pressure inside the hollow portion of the base body is controlled.

The diameter and length of the pipe are, for example, 25 μmφ to 25 μm, respectively.
It can be 2000 μmφ and 5 mm to 300 mm.

According to this example, the air discharge speed within the hollow portion 4c can be adjusted by both the diameter and length of the pipe. Also,
Even after the size of the small through hole 5e has been set once, the air discharge speed can be readjusted by adding a new pipe 19 or cutting off one end of the pipe 19 by a predetermined length. It's easy to do.

FIG. 5 on the left is an enlarged sectional view of a main part showing still another coating device.

A through hole 5b is provided in the lid 5, and a sintered metal body 16 is fitted into the through hole 51. By changing the material and diameter of this force 1L compaction body 16, the pressure within the hollow portion of the base body is controlled.

In addition, it is also possible to mold the lid 5 entirely from sintered metal, and it is also possible to mold all M5 except for the handle 5a from sintered metal.

According to this example, since a sintered metal body is used, sintered metal bodies of various shapes can be easily created. In addition, by selecting the sintering conditions, etc., the size of the pores in the sintered metal body can be varied, and the resistance to the initial appearance of gas and the gas discharge rate can be easily changed or set to various values. .

1 FIG. 6 is a sectional view showing still another coating device.

In this example, the lid 5 is not provided with a pipe for venting air, but is provided with a pipe 9 that penetrates the bottom surface 2c of the coating tank.

The height of the upper end 9a of the pipe is made higher than the level of the coating liquid to prevent leakage of the coating liquid from the pipe 9. A needle valve 8 is provided in the pipe 9.

In this example as well, the needle valve 8 controls the pressure inside the hollow portion of the base body, as in the first embodiment. In addition, since the pipe 9 and needle valve 8 are not provided on the lid 5 side, but are provided on the coating tank 2 side, the conventional lid 5 can be used as is, and a gas exhaust means is provided on the lid 5 for each base drum. There is no need to

FIG. 7 is a schematic partial sectional view showing still another coating device, which is of a so-called overflow type.

Also in this example, the pipe 9 is provided with the needle valve 8, and the same effects as in the first embodiment can be achieved.

A predetermined coating liquid 1 is stored in the coating tank 2, and a tray 13 is provided around the side wall 2d of the coating tank 2. The coating liquid 1 is sent out from the tank 12 by the pump (P) 17, is supplied through the filter 15 into the coating tank 2 from the supply port 11 as shown by the arrow E, and is further supplied to the side wall 2d.
overflows in the circumferential direction of the coating tank 2 over the upper edge 2e,
It is collected in the receiving & J tray 13 and discharged into the tank 12 through the discharge port 14. The cylindrical base drum 4 is immersed in the coating liquid 1, and then the base drum 4 is pulled up at a predetermined speed to perform dip coating. When applying this dip, do you apply it as described above? Since Fl 1 continues to overflow over the upper edge 2e of the side wall 2d, the level of the coating liquid 1 is kept constant.

According to this overflow one-type coating method, since the liquid level is kept constant in the coating device, there is no formation of dry solids on the inner wall of the coating tank, and even if they are formed, they can be filtered by the filter 15, so that foreign substances can be removed. Effective in preventing coating defects due to adhesion.

FIGS. 8 to 10 each show an example of an electrophotographic photoreceptor on which layers are formed by the coating apparatus of the present invention.

In the photoreceptor shown in FIG. 8, a first
A carrier generation layer 31 is provided as a layer, and a -V carrier transport layer 32 is provided as a second layer on the carrier generation layer 31. The photoreceptor shown in FIG. 9 has a carrier transport layer 32 as a first layer and a carrier generation layer 31 as a second layer stacked in this order when viewed from the conductive substrate 30 side. 1st
The photoreceptor shown in FIG. 0 has, as a first layer, a photosensitive layer 33 having a single-layer structure containing both a Toyaria-generating substance and a Toyaria-transporting substance.

Of course, the number and types of coating layers coated and formed by the coating apparatus of the present invention are not limited to the examples shown in FIGS. 8 to 10, nor are their compositions, functions, etc. It can be set freely according to the design intention.

For example, when viewed from the conductive substrate side, the first layer and the second layer are a subbing layer, a photosensitive layer with a single layer structure, a photosensitive layer with a single layer structure,
A protective layer, a first layer, a second layer, and a third layer are a subbing layer, a carrier transport layer, and a carrier generation layer, respectively.
carrier generation layer, carrier transport layer, protective layer;
The first layer, the second layer, the third layer, and the fourth layer are each a subbing layer, a carrier generation layer, a carrier transport layer, and a protective layer, or a subbing layer, a carrier transport layer, a carrier generation layer, and a protective layer. Examples include those that are.

The undercoat layer is acrylic, methacrylic, vinyl chloride,
Vinyl acetate-based, epoxy-based, polyurecne-based, phenol-based, polyester-based, alkyd-based, polycarbonate-based, silicone-based, melamine-based, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, etc. It can be formed from various resins.

The carrier generation layer is made of, for example, a monoazo dye, a disazo dye,
Azo dyes such as trisazo dyes, perylene dyes such as perylene anhydride and perylene imide, indigo dyes such as indigo, thioindigo, polycyclic quinones such as anthraquinone, pyrenequinone and furapanthrones, quinacridone dyes, Eutectic complexes formed from phthalocyanine pigments such as bisbenzimidazole pigments, induthrone pigments, squarelillium pigments, metal phthalocyanines, metal-free phthalocyanines, pyrylium salt pigments, deapyrylium salt pigments, and polycarboim-1. It can be formed by dissolving and shallowly dispersing a variety of known toxin-generating substances in a solvent together with a suitable binder resin and, if necessary, a carrier transport substance, and coating the mixture.

The carrier transport layer may be made of an electron-accepting substance that easily transports electrons, such as trinitrofluorenone or υ; Polymers having ring compounds in their side chains, triazole derivatives, oxylydiazole derivatives, imidazole derivatives, birapurine derivatives, polyarylalkane derivatives, phenylenediamine derivatives,
Various known carrier transport substances that easily transport holes, such as hydrazone derivatives, amine-substituted chalcone derivatives, triarylamine derivatives, carbazole derivatives, stilhen derivatives, and phenothiazine derivatives, are dissolved in a solvent together with an appropriate binder resin, applied, and dried. can be formed.

Further, a photosensitive layer having a single layer structure can be formed by dissolving or dispersing the carrier generating substance as described above in a solvent together with a suitable carrier transporting substance and a binder resin, and coating the solution.

Examples of the binder resin include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, and styrene copolymer resins (e.g., styrene-butadiene copolymer, styrene-methyl methacrylate). copolymer), acrylonitrile), IJ-based copolymer resin (e.g. vinylidene chloride-acrylonitrile copolymer, etc.), vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone - alkyd resins, phenolic resins (e.g. phenol-formaldehyde resins, m-cresol-formaldehyde resins, etc.), styrene-alkyd resins, poly-N-vinylcarbazole, polyvinyl butyral,
Film-forming polymers such as polyvinyl formal are preferred.

In addition, the protective layer contains polyurethane, polyethylene, polypropylene, etc. as the carrier transporting substance and binder resin.
Acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, phenol resin, polyester resin, polycarbonate resin, silicone resin, melamine resin, etc., and copolymers containing two or more repeating units of these resins. It can be formed from resin or the like.

Solvents used in coating and forming the carrier transport layer, carrier generation layer, etc. include acetone, methyl ethyl ketone, cyclohexanone, Hensen, 1-ruene, 2-1
-Silene, chloroborum, dichloromethane, 12-dichloroethane, 112-trichloroethane, 1,1,2.
2-tetrachloroethane, 112-trichloropropane, 1°1.2.2-tetrachloropropane, 1,2.3
Trichloropropane, 1,1.2-)dichlorobutane,
1,23.4-tetrachlorobutane, tetrahydrofuran, monochloromenzene, dichloromenzene, dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methylcellosolve acetate, n-butylamine, diethylamine, Examples include ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, and NN-dimethylformamide.

Further, as a solvent for dissolving the carrier transport substance and the binder resin to form a coating liquid, a solvent is selected that can uniformly dissolve these materials, and a solvent with a boiling point (b p) of 80% is selected.
°C to 150 °C is preferable, and 90 °C to 120 °C
°C is more preferred. If the boiling point is less than 80° C., drying is too fast, resulting in dew condensation and brushing, and drying is too fast, making leveling impossible and making it difficult to obtain a smooth photosensitive layer. Furthermore, if the temperature exceeds 150°C, dripping and uneven coating are likely to occur. Specifically, dichloromethane, 1. −
2-dichloroethane (bp=83.5°C), 1,1.
2-) dichloroethane (bp-113, 5°C), 1.
4-dioxane (bp=101.3°C), Hensen (
bp = 80.1°C), toluene (bp = 110.
6'C), o, m, p, -xylene (b p = 13
8-144°C), tetrahydrofuran, dioxane,
Examples include monochlorhenzene and the like. Also, the boiling point is 80
Even if the temperature of the solvent is not within the range of 150°C to 150°C, the boiling point can be adjusted by mixing a high boiling point solvent and a low boiling point solvent.

Further, as a solvent for forming a carrier generation layer and a photosensitive layer having a single layer structure, it is necessary to dissolve the binder resin and the carrier transport substance contained if necessary, and to transfer the carrier generation substance to a particle size of preferably 2 μm or less, more preferably 1 μm or less. A material that can be dispersed in the form of fine particles and provide a stable dispersion, and that does not unduly dissolve or swell the underlying carrier transport layer, subbing layer, etc., if present, is selected.

In particular, among the above, toluene, chloroform, dichloromethas 1,2-dichloroethane, 1,12-trichloroethane, 1,1,2,2-tetrachloroethane, tetrahydrofuran, monochlorohenzene, and dioxane are used in the carrier generation layer, carrier It is a preferred solvent for both transport layers.

The coating liquid used in the present invention may contain other substances in addition to those mentioned above. For example, the inclusion of a cyrogisan compound has the effect of smoothing the coated surface. Examples of the siloxane compounds include dimethylpolysiloxane and methylphenylpolysiloxane.

The amount added is preferably 1 to 110,000 pp, more preferably 10 to 11,000 pp with respect to the total amount of the coating liquid.

Further, in the photosensitive layer, for the purpose of reducing residual potential and memory, an electron-accepting substance such as succinic anhydride, maleic anhydride, or phthalic anhydride is preferably added to the carrier-generating substance 1.
It can be added in a proportion of 0.1 to 100 parts by weight per 00 parts by weight. Furthermore, the photosensitive layer may contain an organic amine such as butylamine or diisobutylamine in a mole number equal to or less than that of the carrier-generating substance, if necessary, for the purpose of improving sensitivity and reducing memory.

In addition, it is also possible to form a photoreceptor using the same binder resin and the same solvent, especially in the coating liquid for the carrier transport layer and the coating liquid for the carrier generation layer. In that case, the productivity and performance of the photoreceptor may be improved. This has the advantage of further improving the performance. Immediately,
If the same binder resin can be used, the barrier between the carrier generation layer and the carrier transport layer will be reduced, and the carrier generated on the light irradiation layer will be injected and transported to the -1-layer transport layer B to the photoreceptor. The sensitivity characteristics, residual potential, memory characteristics, etc. are also improved.

Furthermore, if the same binder resin, solvent, etc. can be used in common, there is an advantage that the coating process becomes easier, more accurate, and faster.

The shape and material of the conductive substrate are not particularly limited. However, a V-cylindrical shape is preferably used.

Materials include aluminum 1"71, metal plate such as alloy, metal drum J1, conductive polymer, conductive compound such as indium oxide, or conductive thin film made of aluminum lamination J8, palladium, gold, etc. Paper, plastic film 1,
A device that is provided on a harmful body such as the following is used.

More specifically, the following method is selected for forming the carrier generation layer and the photosensitive layer having a single layer structure.

(a) A method of applying a solution in which a carrier-generating substance is dissolved in a suitable solvent, or a solution in which a binder is added and mixed and dissolved.

(b) A method in which a carrier-generating substance is made into fine particles in a dispersion medium using a ball mill, a homogenizer, etc., and a binder is added as needed to mix and disperse the obtained dispersion, and the resulting dispersion is applied.

Dispersing the particles under the action of ultrasound in these methods allows for homogeneous dispersion.

The viscosity of the coating liquid for forming photoreceptor constituent layers such as the photosensitive layer, undercoat layer, and protective layer is preferably within the range of 5 to 500 cp (centivoise), and more preferably within the range of 10 to 300 cp. preferable. If the viscosity is smaller than the above range, the coating film tends to sag, and the film tends to be thicker at the bottom than at the top.If the viscosity is larger than the above range, the viscosity of the coating solution in the coating tank will be uneven. This tends to cause uneven coating film thickness.

In addition, when forming the photoreceptor constituent layers, blade coating,
Coating methods such as spray coating and spiral coating may also be used in combination.

Although the present invention has been illustrated above, the embodiments of the present invention are not limited to the above embodiments, and various modifications are possible.

For example, the dimensions, shapes, numbers, etc. of the coating tank, gas discharge pipe, small through holes, etc. can be modified in various ways.

The gas evacuation methods described in FIGS. 1 and 3 to 6 can be applied to the overflow type coating apparatus shown in FIG. 7. Further, in FIG. 1, the pipe 9 can be provided with two or more needle valves 8, and the pipe 9 can be made to have two or more M5s passing through it. In Fig. 3, the small through hole 5d
It is also possible to provide two or more, and the same applies to FIGS. 3 to 7.

The needle valve 8 shown in FIG. 1 and the small through hole 5d shown in FIG. 3 can be used together, and the same applies to FIGS. 4 to 7.

Instead of the sintered metal body 16 shown in FIG. 5, it is also possible to use a ceramic porous body, a natural porous body such as pumice, a multi-plate, a mesh, or the like.

The present invention can be applied to various coating devices.

6. Effects of the Invention The coating device of the present invention is equipped with a gas discharge hole for discharging the gas in the recessed portion when the object to be coated is immersed. Therefore, it is possible to prevent the gas in the recess from leaking into the coating liquid and forming bubbles. This can prevent the coating solution from shaking and cause uneven coating, and can form a uniform coating.

Furthermore, the gas discharge hole itself has the function of discharging the gas within the recess according to its pressure.

Therefore, there is no need to add a complicated operation from the outside to discharge the gas in the recess, which is simple and requires no effort.

Furthermore, since the exhaust gas is configured to be discharged into an open system outside the coating tank, there is no need for additional equipment such as a separate air chamber outside the coating tank, and the entire device is therefore simpler. and does not take up much space.

[Brief explanation of the drawing]

Figures 1 to 7 show examples, where Figure 1 is a sectional view showing the coating device, Figure 2 is a sectional view showing the coating tank, and Figure 3(a) is another coating device. FIG. 4 and FIG. 5 are enlarged sectional views of essential parts showing still another coating device, and FIG. 6 is an enlarged sectional view of essential parts showing another coating device. FIG. 7 is a schematic partial sectional view showing a so-called overflow type coating device. FIG. 8, FIG. 9, and FIG. 10 are partial sectional views each showing an example of an electrophotographic photoreceptor. FIG. 11, FIG. 12, and FIG. 13 are sectional views each showing a conventional coating device. In addition, in the symbols shown in the drawings, 1... Coating liquid 1b, Ic, le, 1f... Position (height) of coating liquid level 2...
...... Coating tank 4 ...... Conductive substrate tram 4b, 4f...
......Opening 4c...Base drum hollow part 5...
......Lid 5a...Handle 5b...Through holes 5d, 5e...Small through hole 8...
...Needle valve 9.19...Pipe 10...
...0-ring 18...Valve with on-off valve 28...
...It is an air chamber.

Claims (1)

[Claims] 1. Applying the coating liquid to the object by immersing the object having a concave portion in a coating liquid contained in a coating tank and lifting the object to be applied relative to the application liquid. The coating device is provided with a gas discharge hole which itself has a function of discharging the gas in the recess according to the pressure of the gas when the object to be coated is immersed,
A coating apparatus characterized in that the discharged gas is discharged into an open system outside the coating tank.